This invention relates in general to emergency locking safety belt retractors for vehicles wherein the safety belt allows freedom of movement of the passenger under the tension of the retractor rewind spring subject to locking up in the event of an emergency condition, and more specifically to means for reducing the tension applied to the belt when in use due to the retraction spring bias upon the belt.
Various types of safety belt harnesses employing various safety belts and straps are currently in use in automotive and air vehicles for restraining passengers in their seats in the event of an emergency condition. It is common practice to employ safety belt retractor devices in association with such harnesses and belt systems in order to store the belt or webbing when it is not in use. Because of the rewind spring employed to rewind the belt into the retractor, there is a certain tension applied by the rewind spring to the belt when it is placed about the passenger in use. It has been recognized heretofore that such tension can be objectionable to the vehicle passenger and various means have been employed heretofore for relieving or reducing the tension of the rewind spring on the belt when in use. One such prior attempt is disclosed in the prior U.S. Pat. No. 3,834,646 in which belt tension is completely relieved by means activated by a belt manipulation to hold the belt storage reel against retraction. However, it has been found to be desirable to have a low tension bias on the belt toward a rewind condition in order to avoid a slack belt condition and to facilitate employing means for automatically retracting the belt if it is merely disconnected when in the so-called "comfort zone" condition when the reduced tension is in affect.
In my prior co-pending U.S. patent application Ser. No. 635,413, filed Nov. 26, 1975, I have disclosed tension relieving means for safety belt retractors wherein additional means are provided for applying a low tension upon the safety belt when the bias of the main rewind spring is blocked from acting upon the belt. In my co-pending application Ser. No. 714,395 filed Aug. 16, 1976, I have disclosed a tension relieving means which employ a single spring for biasing the reel in both main rewind and low tension rewinding modes, with means for selectively applying a portion of the rewind torque of the safety belt retractor rewind spring back on to the retractor spool in a belt unwinding direction to produce a reduced torque "comfort zone" condition for the belt when it is placed in use and manipulated in a predetermined manner, more specifically in response to a slight retraction movement of the belt following an initial protraction thereof. In each of these prior retractors having a "comfort zone" effect, the extent of belt movement while under the effect of the reduced tension has been somewhat limited.